Effects of dry heat and saturated steam on the physical properties of chitosan

✍ Scribed by Lim, Lee-Yong ;Khor, Eugene ;Ling, Chiew-Eng

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 118 KB
• Volume: 48
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/(sici)1097-4636(1999)48:2<111::aid-jbm3>3.0.co;2-w

✦ Synopsis

Heat may be employed to facilitate the processing of chitosan and to confer sterility on chitosan-based medical products. In this study, changes were analyzed of the physical properties of purified chitosan heated at 60 to 160 degrees C under specified conditions for periods ranging from 0.5 to 4 h. Two forms of heat were used for processing: dry heat generated by a convection oven and saturated steam generated by an autoclave. Dry heat at < or = 80 degrees C resulted in less rigid chains with lower glass transition temperature, improved aqueous solubility, and slightly higher [eta]. At higher temperatures, dry heat produced chromophores, which may be related to interchain crosslink formation involving the NH2 groups. The [eta] and aqueous solubility of the samples decreased with temperatures > or = 120 degrees C. The coloration of the samples intensified from yellow to brown with increasing temperatures and duration of heat exposure. Chitosan heated at 160 degrees C for > or = 2 h was insoluble in the 0.2 M acetic acid/0.1 M sodium acetate solvent. The rate and extent of the thermal reactions were increased in the presence of saturated steam; the autoclaved samples became insoluble after 2 h of heating at 115 degrees C and after 1 h at > or = 120 degrees C. On the other hand, the physical changes induced by dry heat at < or = 120 degrees C were not affected significantly by heating the chitosan samples under anoxic conditions.